Nobody makes anything like that for the 4Runner. Your best bet would be to find a Flippac or Wildernest for a compact truck, hack it up, and graft it onto the 4Runner fiberglass. Might be easier to find a Chinook camper conversion and put that on the 4Runner instead? Here's a couple I really like. One is on a Landcruiser, but you get the idea.
KidVermicious, I have been searching for several months for the perfect Chinook. I have also played with the idea of hacking up another rig and moving the shell like Ibrisoffroad did:
Isn't it always? It doesn't have to be a Chinook, any camper will do. These two are custom, but they're both the size of a regular camper. Here's one on a Mercedes: